Artificial hair fibers

ABSTRACT

An artificial hair fiber suppressed in formation of nodes is provided. An artificial hair fiber is structured with a fiber of drawn resin composition; wherein: when an initial tensile stress of undrawn fiber at 100° C. is taken as F0, and a tensile stress when drawn by 2.5 times is taken as F1, F1/F0 of an undrawn fiber obtained by spinning the resin composition is 1.2 or more.

TECHNICAL FIELD

The present invention relates to a fiber used for artificial hair capable of being attached and detached onto head, such as wig, hair-wig, hairpiece and the like (hereinafter referred to as “artificial hair fiber”).

BACKGROUND

Patent Literature 1 discloses an artificial hair fiber obtained by threading a resin composition including polyamide and bromine-based flame retardant.

CITATION LIST Patent Literature

[Patent Literature 1] JP 2011-246844A

SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, the artificial hair fiber is prepared by drawing a thread of undrawn fiber formed by melt spinning. However, when the thread is not drawn uniformly during drawing, a knot-like node can be formed in the thread after drawing. When the node exists in the artificial hair fiber it can cause problems such as inferior texture.

The present invention has been made by taking the afore-mentioned circumstances into consideration. The present invention provides an artificial hair fiber suppressed in formation of nodes.

Solution to Problem

According to the present invention, an artificial hair fiber structured with a fiber of drawn resin composition; wherein: when an initial tensile stress of undrawn fiber at 100° C. is taken as F0, and a tensile stress when drawn by 2.5 times is taken as F1, F1/F0 of an undrawn fiber obtained by spinning the resin composition is 1.2 or more, is provided.

The present inventors have performed extensive research and have found that when artificial hair fiber is manufactured by drawing undrawn fiber having F1/F0 of 1.2 or more, artificial hair fiber suppressed in generation of nodes can be obtained, thereby accomplishing the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention will be explained.

The artificial hair fiber of the present embodiment is structured with a fiber obtained by drawing a resin composition. When the initial tensile stress of the undrawn fiber is taken as F0, and the tensile stress when drawn by 2.5 times is taken as F1,

F1/F0 of the undrawn fiber obtained by spinning the resin composition (hereinafter referred to as “F1/F0 of resin composition”) is 1.2 or more.

Resin Composition

The tensile stress of the undrawn fiber obtained by spinning the resin composition can be measured under the following conditions of temperature: 100° C., chuck-chuck distance: 100 mm, tension speed: 0.5 m/min. The initial tensile stress F0 is a tensile stress immediately after starting the measurement (more precisely, when the undrawn fiber is elongated by 1%), and the tensile stress when drawn by 2.5 times F1 is a tensile stress when the undrawn fiber is drawn by 2.5 times.

F1/F0 is an indicator which shows the increase in tensile stress due to drawing. The larger the value of F1/F0, the extent of increasing tensile stress due to drawing (extent of strain hardening) becomes larger. When the value of F1/F0 is large, the portion having lower extent of drawing tends to be drawn. Since the portion having low extent of drawing results in node, generation of nodes can be suppressed by using undrawn fiber having large F1/F0. Particularly, when F1/F0 is 1.2 or more, generation of nodes can be suppressed, and when F1/f0 is 1.3 or more, generation of nodes can be further suppressed. F1/F0 is further preferably 1.4 or more. The upper limit of F1/F0 is preferably 2.0 or lower, more preferably 1.8 or lower, and further preferably 1.6 or lower. In such case, speed of melt spinning during manufacture can be increased, thereby being superior in productivity.

Base Resin

The resin composition which structures the artificial hair fiber of the present embodiment contains a base resin, and arbitrarily contains additives such as flame retardant and the like. The base resin is preferably contained in the resin composition by 50 mass % or more, more preferably 80 mass % or more. In such case, melt forming of the resin composition becomes easy.

F1/F0 of the undrawn fiber obtained by spinning the base resin (hereinafter referred to as “F1/F0 of base resin”) is preferably 1.3 or more, more preferably 1.4 or more. In such case, the value of F1/F0 of the resin composition tends to become large. F1/F0 of the base resin is preferably 2.0 or lower.

The composition of the base resin of the resin composition according to the present embodiment is not particularly limited. The base resin is preferably composed of at least one selected from the group consisting of polyamide, polyester, and vinyl chloride. The base resin preferably includes polyamide by 50 mass % or more, more preferably by 80 mass % or more. In such case, artificial hair fiber having superior heat resistance and texture can be obtained easily.

Polyamide preferably includes aliphatic polyamide, and can include aliphatic polyamide and semi-aromatic polyamide which has a skeleton obtained by condensation polymerization of aliphatic diamine and aromatic dicarboxylic acid. Preferably, polyamide includes aliphatic polyamide by 50 mass % or more, and more preferably, the base resin includes aliphatic polyamide by 50 mass % or more. In such case, texture of the artificial hair fiber is particularly superior.

Aliphatic polyamide is polyamide which does not have aromatic ring. As the aliphatic polyamide, n-nylon which is formed by ring-opening polymerization of lactam, and n,m-nylon which is synthesized by co-condensation polymerization reaction of aliphatic diamine and aliphatic dicarboxylic acid can be mentioned. As the aliphatic polyamide, for example, polyamide 6 and polyamide 66 can be mentioned. In terms of heat resistance, polyamide 66 is preferable.

As the semi-aromatic polyamide, for example, polyamide 6T, polyamide 9T, polyamide 10T, and modified polyamides which have monomers for modification copolymerized with these polyamides such as modified polyamide 6T, modified polyamide 9T, and modified polyamide 10T can be mentioned. Among these, in terms of easy melt forming, polyamide 10T is preferable.

Polyester is, for example, PET.

The base resin preferably includes a first resin, and F1/F0 of an undrawn fiber obtained by spinning the first resin (hereinafter referred to as “F1/F0 of first resin”) is preferably 1.3 or more. in such case, F1/F0 of the resin composition tends to become large. The content of the first resin in the base resin is 30 mass % or more for example, preferably 50 mass % or more, more preferably 65 mass % or more, and further preferably 80 mass % or more. In such case, F1/F0 of the resin composition tends to become further larger.

The melt viscosity of the first resin measured at 300° C. and a shear rate of 2400 (1/s) is preferably 100 (Pa·s) or more. In such case, the value of F1/F0 of the first resin tends to become large. The melt viscosity of the first resin measured in the afore-mentioned conditions is preferably 110 (Pa·s) or more. In such case, the value of F1/F0 of the first resin tends to become large.

The first resin is preferably polyamide, more preferably aliphatic polyamide, further preferably polyamide 6 or polyamide 66, and even further preferably polyamide 66. In such case, the value of F1/F0 of the first resin tends to become particularly large.

Flame Retardant

The artificial hair fiber of the present invention preferably includes a flame retardant. The flame retardant is preferably a bromine-based flame retardant. The addition amount of the flame retardant with respect to 100 parts by mass of the base resin is preferably 3 to 30 parts by mass, more preferably 5 to 25 parts by mass, and further preferably 10 to 25 parts by mass. In such case, appearance, stylability, and flame retardance of the artificial hair fiber becomes particularly superior.

As the bromine-based flame retardant, for example, brominated phenol condensation product, brominated polystyrene resin, brominated benzyl acrylate based flame retardant, brominated epoxy resin, brominated phenoxy resin, brominated polycarbonate resin, and brominated triazine based compound can be mentioned.

Other Additives

Regarding the resin composition used in the present embodiment, additives such as flame retardant promoter, fine particles, heat resistance improver, light stabilizer, fluorescent agent, antioxidant, antistatic agent, pigment, dye, plasticizer, lubricant and the like can be added as necessary.

Manufacturing Process

Hereinafter, one example of the manufacturing process of the artificial hair fiber will be explained.

The manufacturing method of the artificial hair fiber according to one embodiment of the present invention comprises a melt spinning step, a drawing step, and an annealing step.

Hereinafter, each of the steps will be explained in detail.

Melt Spinning Step

In the melt spinning step, undrawn fiber is manufactured by melt spinning the resin composition. In particular, first, the afore-mentioned resin composition is melt and kneaded. As the apparatus for melting and kneading, various general kneading machines can be used. As the melting and kneading machine, a single screw extruder, a twin screw extruder, a roller, a Banbury mixer, a kneader and the like can be mentioned. Among these, the twin screw extruder is preferable in terms of adjusting the degree of kneading and simple operation. The artificial hair fiber can be manufactured by selecting an appropriate temperature conditions depending on the polyamide, and performing melt spinning by ordinary melt spinning method.

The fineness of single fiber of the artificial hair fiber according to the present embodiment is preferably 20 to 100 decitex, more preferably 35 to 80 decitex. In order to achieve such fineness of single fiber, fineness of fiber immediately after the melt spinning step (undrawn fiber) is preferably adjusted to 300 decitex or lower. When the fineness of the undrawn fiber is small, the drawing magnitude for obtaining artificial hair fiber with low fineness can be made small, thereby suppressing occurrence of gloss in the artificial hair fiber after drawing processing. Accordingly, maintaining a condition ranging between medium gloss to three-quarter gloss tends to be easy.

Drawing Step

In the drawing step, the undrawn fiber obtained is drawn by a drawing magnitude of 1.5 to 5.0 times, thereby manufacturing a drawn fiber. With such drawing, a drawn fiber having low fineness of 100 decitex or lower can be obtained, and tensile strength of the fiber can also be improved. The drawing magnitude is preferably 2.0 to 4.0 times. When the drawing magnitude is sufficiently large, fiber strength tends to be achieved easily, and when the drawing magnitude is sufficiently small, thread breakage during drawing processing tends to be suppressed.

The temperature during the drawing processing is preferably 90 to 120° C. When the temperature during the drawing processing is too low, the fiber strength tends to become weak and thread breakage tends to occur easily. When the temperature of the drawing processing is too high, the texture of the fiber obtained tends to be close to those of plastic, and feels slippery.

Annealing Step

In the heat annealing step, the drawn fiber is subjected to heat treatment at a heat treatment temperature of 150 to 200° C. With this heat treatment, thermal shrinkage of the drawn fiber can be suppressed. The heat treatment can be performed following the drawing processing, or can be performed some time after the drawn fiber is wound. The heat treatment temperature is preferably 160° C. or higher, more preferably 170° C. or higher, and further preferably 180° C. or higher.

EXAMPLES Manufacture of Artificial Hair Fiber of Examples and Comparative Examples

Polyamide dried so as to have a moisture content of less than 1000 ppm, PET, and bromine-based flame retardant were blended so as to have a formulation ratio shown in Table 1. The numerical values of the formulation amount regarding the polyamide, PET, and bromine-based flame retardant shown in Table 1 are represented as parts by mass. The blended material was melted and kneaded using a twin-screw extruder having φ40 mm at a barrel temperature of 280° C. Thereafter, jetting amount of the material was adjusted to be constant using a gear pump, and the material was molten spun at 295° C. from a dice having a hole diameter of 0.5 mm/hole in a vertical direction. The undrawn fiber was wound at a constant speed using a haul-off machine arranged at a point of 2 m directly below the nozzle. With the undrawn fiber thus obtained, ratio of initial tensile stress F0 and tensile stress when drawn by 2.5 times F1, F1/F0 was measured in accordance with the evaluation criteria described later. The results are shown in Table 1.

The undrawn fiber obtained was drawn at 100° C., followed by annealing at 180° C., thereby obtaining an artificial hair fiber having a desired fineness. The drawing magnitude was 2.3 times, and the relaxation rate during annealing was 6 to 7%. The relaxation rate during annealing is a value obtained by (rotation speed of winding roller during annealing)/(rotation speed of feeding roller during annealing).

With the artificial hair fiber thus obtained, drawing property was evaluated in accordance with the evaluation method and criteria described later. The results are shown in Table 1.

In addition, with three kinds of PA66 shown in Table 1, melt viscosity was measured. The results are shown in Table 2.

TABLE 1 Comparative Example Example Table 1 1 2 3 4 5 6 7 1 2 composition PA66 A 80 20 45 45 45 B 80 80 C 20 20 55 100 80 PA6 80 PA1OT 55 PET 55 bromine-based flame retardant 20 20 property F1/F0 1.45 1.40 1.38 1.32 1.26 1.24 1.22 1.07 1.03 melt viscosity (Pa·s) 143 130 143 110 105 111 120 75 68 evaluation drawing by number of node 2 3 4 4 6 6 9 20 or 20 or of drawing 2.5 times (per 10 m of more more one fiber) property drawing by number of node 1 1 2 3 4 4 5 11 13 4.0 times (per 10 m of one fiber)

TABLE 2 shear rate melt viscosity(Pa · s) (1/sec) A B C 6.1E+01 1129.2 929.0 433.8 1.2E+02 803.4 671.2 324.7 2.4E+02 548.7 470.5 217.7 6.1E+02 352.2 305.5 141.1 1.2E+03 241.2 208.6 102.0 2.4E+03 163.4 145.0 74.6 6.1E+03 91.0 82.1 49.3 1.2E+04 57.0 52.9 36.3

As the materials mentioned in Table 1 and Table 2, the followings were used. The melt viscosity in the following list are values measured at 300° C. and a shear rate of 2400 (1/s).

PA66(A): product of Denka Company Limited, F1/F0 =1.55, melt viscosity 163 (Pa·s)

PA66(B): product of Denka Company Limited, F1/F0 =1.54, melt viscosity 145 (Pa·s)

PA66(C): product of Denka Company Limited, F1/F0 =1.07, melt viscosity 75 (Pa·s)

PA6: product of Denka Company Limited, F1/F0 =1.46, melt viscosity 130 (Pa·s)

PA10T: available from Daicel-Evonik Ltd., VESTAMID HO Plus M3000, F1/F0 =1.16, melt viscosity 68 (Pa·s)

PET: available from Mitsui Chemicals, Inc., J125S, F1/F0 =1.14, melt viscosity 67 (Pa·s) bromine-based flame retardant: available from Sakamoto Yakuhin Kogyo Co., Ltd., brominated epoxy resin SRT-20000

Various Measurement⋅Evaluation

Measurement and evaluation of various characteristics and properties were performed by the method shown below.

Tensile Stress

The tensile stress of Examples and Comparative Examples were measured using STROGRAPH T (available from Toyo Seiki Seisaku-sho, Ltd.) under conditions of 100° C. temperature, 100 mm chuck-chuck distance, 0.5 m/min tension speed, and 125 pm fiber diameter. The initial tensile stress F0 is a tensile stress immediately after starting the measurement (more precisely, when the undrawn fiber is elongated by 1%), and the tensile stress when drawn by 2.5 times F1 is a tensile stress when the undrawn fiber is drawn by 2.5 times.

Melt Viscosity

The melt viscosity of Examples and Comparative Examples were measured using Capilograph 1D (available from Toyo Seiki Seisaku-sho, Ltd.) at 300° C. and shear rate shown in Table 2, in accordance with JIS K 7199.

Evaluation of Drawing Property

With the artificial hair fiber prepared by drawing magnitude of 2.5 times or 4 times, number of nodes per 10 m of one fiber was counted by visual observation.

Discussion

With all the Examples having F1/F0 of 1.2 or more, the drawing property was superior, and with all the Comparative Examples, the drawing property was not good. Further, with Examples 1 to 4 which had F1/F0 of 1.3 or more, the drawing property was particularly superior. 

1. An artificial hair fiber structured with a fiber of drawn resin composition; wherein: when an initial tensile stress of undrawn fiber at 100° C. is taken as F0, and a tensile stress when drawn by 2.5 times is taken as F1, F1/F0 of an undrawn fiber obtained by spinning the resin composition is 1.2 or more.
 2. The artificial hair fiber of claim 1, wherein: the resin composition comprises a base resin including a first resin; and F1/F0 of an undrawn fiber obtained by spinning the first resin is 1.3 or more.
 3. The artificial hair fiber of claim 2, wherein the first resin in the base resin is contained by 50 mass % or more.
 4. The artificial hair fiber of claim 2, wherein the first resin is polyamide.
 5. The artificial hair fiber of claim 3, wherein the first resin is polyamide. 